/*******************************************************************************
 * Copyright (c) 2001, 2005 IBM Corporation and others. All rights reserved. This program and the
 * accompanying materials are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html Contributors: IBM Corporation - initial API and
 * implementation Jens Lukowski/Innoopract - initial renaming/restructuring
 *******************************************************************************/
package org.eclipse.wst.sse.ui.internal.util;

/**
 * The SortOperation takes a collection of objects and returns a sorted collection of these objects.
 * Concrete instances of this class provide the criteria for the sorting of the objects based on the
 * type of the objects.
 */
public abstract class Sorter {

  /**
   * Returns true if elementTwo is 'greater than' elementOne This is the 'ordering' method of the
   * sort operation. Each subclass overides this method with the particular implementation of the
   * 'greater than' concept for the objects being sorted.
   */
  public abstract boolean compare(Object elementOne, Object elementTwo);

  /**
   * Sort the objects in sorted collection and return that collection.
   */
  private Object[] quickSort(Object[] sortedCollection, int left, int right) {
    int originalLeft = left;
    int originalRight = right;
    Object mid = sortedCollection[(left + right) / 2];

    do {
      while (compare(sortedCollection[left], mid))
        left++;
      while (compare(mid, sortedCollection[right]))
        right--;
      if (left <= right) {
        Object tmp = sortedCollection[left];
        sortedCollection[left] = sortedCollection[right];
        sortedCollection[right] = tmp;
        left++;
        right--;
      }
    } while (left <= right);

    if (originalLeft < right)
      sortedCollection = quickSort(sortedCollection, originalLeft, right);
    if (left < originalRight)
      sortedCollection = quickSort(sortedCollection, left, originalRight);

    return sortedCollection;
  }

  /**
   * Return a new sorted collection from this unsorted collection. Sort using quick sort.
   */
  public Object[] sort(Object[] unSortedCollection) {
    int size = unSortedCollection.length;
    Object[] sortedCollection = new Object[size];

    //copy the array so can return a new sorted collection
    System.arraycopy(unSortedCollection, 0, sortedCollection, 0, size);
    if (size > 1)
      quickSort(sortedCollection, 0, size - 1);

    return sortedCollection;
  }
}
